CIALDI, ALESSANDRO. — Navigator and scholar of hydraulic and nautical sciences, pontifical naval officer, born in Civitavecchia on 9 April 1807, died in Rome on 16 June 1882. In 1840, with the rank of captain and in command of a small naval squadron, he was the first to sail up the Nile with European vessels for 1,164 km from its mouth; after having the name of Gregorio XVI carved on the Temple of Isis on the island of Philae, he returned to Rome (28 August 1841), bringing a valuable collection of archaeological, nautical, and natural-scientific materials and information, together with four large alabaster parallelepipeds donated by the viceroy of Egypt to the Pontiff for the reconstructed basilica of S. Paolo fuori le mura.
It was thanks to C. that a modest but well-organized and well-led pontifical fleet was able in 1848 to operate successfully in the Adriatic alongside the other Italian fleets against the Austrian one, and in 1860 to supply the fortress of Ancona promptly with arms and ammunition, when it was already on the point of being besieged. In 1867 he wisely thwarted daring Garibaldian attempts at raids and landings along the coasts of Lazio and on the course of the Tiber, such as that of the Cairoli brothers; nor did C. and his sailors remain inactive in 1870 in the face of the rapid precipitate course of events.
From then on, remaining faithful to the Pontiff, he withdrew into private life in order to devote himself to his favorite studies. These included the regulation of the courses of the Tiber and the Serchio; improvement and modernization works in the ports of Livorno, Genoa, Pesaro, Civitavecchia, Fiumicino, and Anzio; the substantial contribution he made in supporting and technically and financially assisting the cutting of the Isthmus of Suez, as well as in directing the works themselves, including as a member of the special pontifical Commission; and the work carried out for the implementation and complete, rational illumination of the coasts and landing places of the Tyrrhenian shores of the Roman State. C.’s principal scientific achievement was the discovery and definitive formulation of the hydrodynamic theory of wave motion and of littoral sea currents. For this reason, on 11 March 1878, the Academy of Sciences of Paris counted him among its members, while he had already belonged, since 1847, to the pontifical Academy of the Nuovi Lincei, of which he became president in 1879, succeeding Angelo Secchi. At his death, C. left the city of Civitavecchia heir to his rich and rare scientific library; in the cemetery of that city he was buried beneath an epitaph composed by the historian of the pontifical navy Alberto Guglielmetti.
Among C.’s works, numbering more than fifty, the following deserve particular mention: Relation de deux voyages exécutés par la marine militaire des Etats Romains dans les années 1840-42, in Annales maritimes et coloniales (Paris 1843); Sul Tevere, sulla linea più conveniente per la unione dei due mari e sulla marina mercantile dello Stato Pontificio (Rome 1847); Sul moto ondoso del mare e sulle correnti di esso specialmente su quelle litorali (ibid. 1843; 2nd, greatly enlarged ed., ibid. 1846); Port Said, A M. F. De Lesseps..., lettre du comm. A. C., etc. (ibid. 1868); Nozioni preliminari per un trattato sulla costruzione dei porti sul Mediterraneo (ibid. 1874); Illuminazione e segnalamento dei litorali e dei porti (ibid. 1878).